Charles Darwin, the main proponent of the theory of evolution based on natural selection, built up much of his evidence for this theory during a five-year voyage around the world. His voyage aboard the H.M.S. Beagle was instrumental not only in the establishment of his theory, but also in the application of the scientific method to the study of nature. Darwin published his theory of evolution in his book "The Origin of Species". His studies were so thorough that the scientific world never challenged his findings. However, his findings were, and continue to be, challenged on philosophical and religious grounds. Darwin's research opened many new lines of inquiry, and inspired a wave of new biological research.